The primary purpose of this project will be the determination of possible differences in bioavailability of molybdenum in food and in water and in the disposition and elemination of what is absorbed. Mo-99 will be used as a tracer. Specifically, the location and kinetics of absorption of molybdenum incorporated in food and as (MoO4) double bond dissolved in water or mixed with food will be determined using everted gut sacs; isolated perfused gut segments; and rats sacrificed serially. In the last group, distribution in tissues and the kinetics of elimination will also be done. This will be supplemented by injection of a dose into the jugular vein and serial sampling of blood from the carotid artery. There is a possibility of changes in molybdate when it is mixed with food in the gut, changes that do not take place when it is given to starved rats in solution. This will be investigated because of its possible influence on the level of retention of molybdenum.